There is no mistaking how much North Korea dislikes Mr John Bolton, the former United States ambassador to the United Nations who last month became US President Donald Trump's third national security adviser.

"We shed light on the quality of Bolton in the past, and we do not hide our feeling of repugnance towards him," said Mr Kim Kye Gwan, North Korea's First Vice-Minister of Foreign Affairs, two weeks ago as it threatened not to attend the June 12 summit.

North Korea does not indeed, having called him "human scum and a bloodsucker" back in 2003.

Mr Bolton was the US undersecretary of state for arms control and international security when North Korea was named in an "axis of evil" with Iraq and Iran by then US President George W. Bush in 2002. In December that year, a pact Pyongyang reached with the Clinton administration to freeze and eventually discontinue its nuclear programme broke down.

Known for his hawkish views, Mr Bolton was a strong proponent inside the Bush administration of the invasion of Iraq and regime change in North Korea.

The man with the bushy moustache is unfazed by North Korea's insults. In his 2007 book, Surrender Is Not An Option: Defending America At The United Nations And Abroad, he said being called human scum by North Korea was the highest accolade he had received during the Bush years.

The North Koreans are no doubt not feeling good about this, but Mr Bolton is back and he has Mr Trump's ear.

With input from US Bureau Chief Nirmal Ghosh